1. Field of the Invention
This invention relates to an electronically controlled carburetor for an internal combustion engine for a vehicle which is effective to electronically control the air bleed amount in response to changes in the air and fuel flows through the venturi thereof and to supply optimum air-fuel mixture to the internal combustion engine.
2. Description of the Prior Art
Heretofore there have been proposed a number of electronically controlled carburetors for the mixture of fuel and air. For example, the prior art carburetor, in trying to control the air-to-fuel ratio of the mixture, has employed the use of an oxygen (O.sub.2) sensor installed in the engine exhaust pipe which is effective to open and close the fuel passage of the carburetor in response to the O.sub.2 -sensing signal, or to drive an air bleed controlling actuator effective to govern the rate of fuel flow. It should be noted that, in such a prior art carburetor, the mixture may be controlled at all times to a theoretical air-to-fuel ratio, because of the sensor responsive to the presence of O.sub.2 in the exhaust gas. However, the mere control of mixture to such a theoretical air-to-fuel ratio has been deemed to be insufficient, because of increasing requirements for minimizing fuel consumption in view of the fuel economy of automotive engines, and also of governmentally imposed limitations on engine exhaust emissions in view of anti-pollution movement.
Furthermore, the prior art electronically controlled carburetor is disadvantageous in that the cooperative oxygen sensor fails to function, because the activating temperature of the sensor is not reached when the engine is cold, and consequently, the carburetor fails to control the air-to-fuel ratio so long as the engine is cold.